Hello? Are You Still There?

Mercury, May/June 2003 Table of Contents

Courtesy of NRAO/AUI/NSF.

by T. Joseph W. Lazio

SETI programs have picked up tantalizing radio signals. Could some of these signals represent genuine transmissions from ET?

Anybody who has experienced a momentary disruption in a cell phone conversation knows that the first task is to verify that the other party is still on the line. Researchers who search for extraterrestrial intelligence (SETI) have found themselves in a similar situation. On a number of occasions they have appeared to be on the tantalizing brink of making first contact with another civilization, only to be unable to verify whether they have found a real signal.

For instance, in August 1977 the Ohio State University "Big Ear" radio telescope picked up what appeared to be a booming ET transmission. Project volunteer Jerry Ehman, who first noticed the powerful signal on a computer printout, was so excited that he scribbled "Wow!" on the paper record of the observation.

More recently, the Planetary Society's Megachannel Extraterrestrial Assay (META) SETI project, operated by Paul Horowitz and colleagues at the Oak Ridge Observatory in Massachusetts, picked up 11 transmissions that exhibit all the hallmarks of being genuine ET signals. Intriguingly, these 11 candidate transmissions tended to be located in or near the plane of the Milky Way's disk, just as one might expect if the transmissions originated from stars in our galaxy.

Unfortunately, all attempts to verify these META candidates or the Wow! signal (or similar candidates from other SETI programs) have failed. As Carl Sagan wrote, "Extraordinary claims require extraordinary evidence." Without more evidence, SETI researchers are unwilling to cite these candidates as evidence of ET transmissions. Before dismissing these candidates too hastily, however, we should consider whether they might represent real ET transmissions that were not subsequently verified because they were modified en route to Earth.

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